Double casing pump



Feb. 9, 1954 E. J. BLACKWELL DOUBLE CASING PUMP Filed OCT.. 26. v1949 high pressure.

Patented Feb. 9, 1954 DOUBLE CASING PUMP Edward J. Blackwell,

Wauwatosa, Wis., assigner to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application October 26, 1949, Serial No. 123,719 4 Claims. (Cl. 10S-109) This invention relates to multiple stage double casing pumps. More specifically this invention relates to that type of double casing pump especially designed for pumping liquids at relatively generally divided by an annular projection into -an intake chamber and a discharge chamber. vThe inner casing is fitted within the outer casing and is seated against the annular projection.

The inner casing contains impellers mounted' within annular passages that direct the liquid through a series of pumping stages, finally passing into the discharge chamber of the outer casing. The inner casing is held tight against the annular seat by the discharge pressure. within the discharge chamber. f

The pumping stages are usually so arranged that the iirst stage takes suction from the intake chamber and discharges to the second stage intake located at the opposite end of the inner casing. This arrangement helps to simplify the problem of sealing the pressure end of the inner casing, since the seal need onlyresist the discharge pressure of the rst stage.

Another serious problem, that of vapor formation, is presented when a pump of this type is used to pump liquids that are highly volatile .either by the very nature of the liquid, or because of the high temperature or .low suction pressure at which theliquid must be handled. The flow of liquid into the iirst stage from the intake chambermust be at a rate s uiiicient to satisfy the demand in order to prevent the formation of a partial vacuum or a reductonin pressure that will cause vapor toform, thus impairing the eiiiciency of the machine. AccordingIy, a primary object ,of the invention is to take in liquid from the intake chamber at a relatively low velocity and satisfy the demand Without the formation of vapor. p

Another object of the invention is to prevent liquid from a higher pressure stage leaking into the intake chamber and flashing into vapor at the reduced pressure and thereby vapor locking the first stage intake.

l Objects and advantages other than those above set forth will be apparent as the description of the invention proceeds.

- 'Ihe novel features of the invention and how 'the objects are attained will appear from vthis specification and the accompanying vdrawing The principal object of this inv -outer casing Il).

showing an embodiment of the invention and forming a part of this application, and al1 these novel features are intended to be pointed out in the claims. Y

Referring to the drawing, the pump comprises an outer casing I divided into an intake chamber II and a discharge chamber I2 separated by an annulaiprojection I3. An inlet passage I4 transmits liquid at intake pressure to the intake chamber II. A discharge passage I5 transmits the liquid from the discharge chamber I2 at discharge pressure. The'outer casing I0 is open at the discharge chamber I2 end of the casing. This open end is fitted with a casing cover I6 which is attached to the outer casing I0 by means of bolts I'I, and a liquid tight seal is insured by a gasket which is set in a Vrecess 2| to avoid the possibility of blowing out. An inner casing 22 isv inserted into the open end of the outer casingll) yand mounted therein. The radial shoulder 23 of the inner casing 22 is seated against the annular projection I3 Within thev outer casing I0. The inner casing 22 is held firmly againstthe projection I3 by the discharge pressure of the liquid within the discharge chamber I2. A gasket 24 is iitted between the shoulder 23 and the projection I3 to provide a liquidtight seal between the intake chamber II andthe discharge chamber I2. Bolts 25 provide an initial seal and keep the inner casing 22 in position during periods of starting and stopping when the pressure within the discharge -chamber I2 may not be enough to maintain the seal. Keys 26, 2l also aid in supporting the inner casing 22 in proper alignment, in that they keep the inner easing 22 lfrom turning within the Ashaft VZtlis disposed 'in the inner casing `22 and extendsi through'both' ends of the outer casing -I0. series of annular passages 29 to direct the iluid through the inner casingl 22.

Impellers'36 to 43 are mounted on the shaft in the annular passages 29 to 35.

The pressure ofthe fluid as it passes through the inner casing 22 is raised in a series of stages herein numbered I through 1. The first stage comprises two impellers 36, 3'I`both of which take suction from the intake. chamber II and discharge into the passages 29 which direct' the liquid to the opposite end of the inner casing 22, where the liquid enters stage 2. The liquid is then directed through the remainder of the stages 2 to 1, which have a single Aimpeller 38 to 43 in each, and the path of the liquid is indicated by '-th'e passages numbered 30 to 35. The

r' fluid passes from the iinal pumping -Istage l-to the passage 35 which discharges into the pressure chamber I2 of the outer casing l0, and the fluid is then discharged from the pump through the discharge passage I5. The axial thrust of the impellers is negated by having an equal number of the impellers facing each end of the pump.

The two impellers 36, 3l, both taking suction from the intake chamber II, are used as the first pumping stage so that a relatively low eye speed at the entrance of the impeller will be maintained. The flow of liquid must keep up with the demand of the rst stage at all times to prevent a reduction in pressure of partial vacuum, which may cause the liquid to vaporize, thereby affecting the operating characteristics of the machine.

The arrangement and location of these two impellers 36, 3l is important in the elimination of all dangers of vapor formation. The impeller 31 is within the inner casing 22 and is wholly Within the discharge chamber I2 of the outer casing Ill. The inlet of the impeller 3l faces the intake chamber II and taking suction therefrom discharges into the passage 29. The

passage 29 is at this point adjacent to the passage 32 having fourth stage pressure therein. The passages 29 and 32 are separated by an annular shaft seal BI. Any leakage of fourth stage pressure that does escape the shaft seal 8I will leak into the passage 29 having first stage pressure. Liquid under fourth stage pressure will not therefore be able to find its way into the intake chamber Il Where the pressure is substantially less than first stage and where there is danger of such liquid hashing into a vapor at the reduced pressure and vapor locking the rst stage intake.

The impeller 36 is mounted within an extending portion 10 of the inner casing 22 and is within the intake chamber II of the outer casing I0. A stuing box member 'II is fitted about the shaft 28 to the outer casing IU and extends through the outer casing I0 into the intake chamber H. An annular sleeve 12 extending from the portion 10 embraces the stu'ing box member I I, thereby supporting the portion 10 in proper axial alignment about the impeller 36.

The arrangement and number of stages as iilustrated results in having between stage I and stage 5, fourth stage pressure in the fluid passage 32 adjacent the passage 29 having first stage pressure therein, and between stage 1 and stage 4, seventh stage pressure in the passage 35 adjacent the passage 3'2 having fourth stage pressure therein. The high differential in pressure at these two locations requires suitable high pressure seals 8l, 82 to reduce leakage of the vhigh pressure liquid into the passage of lower pressure, resulting in a loss of pump 'efliciency The construction of these high pressure sealing arrangements 8l, B2 maybe of the form as here shown and more fully described and claimed in the copending application of Milton W. Lutz, Serial No. 123,856, led October 26, 1949.

A special stuffing bo-x arrangement isprovided, as here shown, for ysealing the Ainner casing 22 to the shaft 28 and to the end cover I6. VThis 'arrangement will .allow axial expansion of the inner casing 22 relative to the outer casing l0 in response to changes 4in pressure and/or tem- .perature within the inner casing '22. When a pump of this general type is used for pumping liquid at high temperature `such as boiler :feed water, the axial .movement .of .the inner casing 22 krelative `to the .outer casing In .may be lllllte substantial and frequent as changes in demand are made upon the pump. To permit this relative movement and yet maintain an effective seal, an annular member 5I is fitted to the inner casing 22 and extends through an opening 6E! in the end cover I6. Glands 52, 53 and packing 55, 56 placed concentrically about and within the member 5I thereby effect a seal between member 5I and the end cover IG, and between the member 5f and the shaft 28. Bolts 6I, t6 keep the glands 52, 53 drawn up tight on the packing 55, 5E to maintain the seal at all times. This stumng box arrangement is described and claimed in the copending application of Hugh L. Ross, Serial No. 123,768,` filed October 26, 1949. It will be understood that as far as the invention of the present application is concerned, means of other form may be provided for sealing the inner casing 22 to the shaft 28 and to the cover I6.

From the forego-ing it will be apparent to those skilled in the art that the illustrated embodiment of the invention provides a new and improved liquid pumping machine and accordingly accomplishes the objects of the invention. On the other hand, it will also be obvious to those skilled in the art that the illustrated embodiment of the invention may be variously changed and modied, or features thereof, singly or collectively, embodied inother combinations than those illustrated, without departing from the spirit of the invention, or sacrificing all of the advantages thereof, and that accordingly the disclosure herein is illustrative only, and the invention is not limited thereto.

It is claimed and desired to secure by Letters Patent:

l. A centrifugal pump comprising: an outer casing having an inlet passageway and an outlet passageway for the flow of liquid therethrough and having an internal wall portion defining an opening; an inner casing in said outer casing cooperating with said wall portion to close said opening and divide said outer casing into separate intake and discharge chambers respectively communicating with said inlet and discharge passageways, said inner casing comprising first, second and third wall parts, said rst Wall part defining a plurality of compartments and intake passages for said liquid, each said compartment communicating with the intake passage hydraulically adjacent theretoand the last of said compartments communicating with said outlet passageway, said second wall part cooperating with said nrst wall part to denne anintermediate passage contiguous to said second wall part and communicating with one of said compartments, said third wall part cooperating with said second wall part to define a pair of vcompartments on the intake chamber ,side of said second Wall part, one compartment of said pair being contiguous to said second wall part and both compartments of said pair communicating with one of said intake passages. .a shaft supported for rotation in said inner casing `and extending through said wall parts; sealing means interposed Vbetween said shaft and said .second wall part; a plurality of single impellers mounted on said shaft, said single impellers being operatively disposed for rotation .in said compartments of .said first wall .part to develop predetermined positive .liquid pressures therein and in said intermediate passage, .and a pair :of impellers mounted yun said shaft `on the intake chamber .side .of said .second `wall part, .o e impeller of said pair -of impellers bei-ng `oper-- fatively disposed in one compartment of said pair ofcompa'rtments and the other impeller of'said r'pair of `impellers being `operatively disposed in the other compartment of said Vpair of compartments, said pair of impellers cooperating to reduce the velocity of liquid flow into said pair `of vcompartments below the velocity of flow in said intake passages and to develop a predeterfmined liquid suction pressure in said, intake :passageway for the flow of liquid therethrough and having an internal Wall portion defining an opening; an innerl casing in said outer casing cooperating with said wall portion to close said opening and divide said outer casing into separate intake, and discharge chambers respectively communicating with said inlet and discharge passageways, said inner casing compris- 'i'ng rst, 'second and third wall'parts, said. first wall part defining a plurality of compartments and intake passages for said liquid, each said compartment communicating with the intake passage hydraulically adjacent thereto and the last of said compartments communicating with said outlet passageway, said second wall part cooperating with said first wall part to define an intermediate passage contiguous to said second wall part and communicating with one of said compartments, said third wall part cooperating with said second wall part to define a pair of compartments on the intake chamber side of said second wall part, one compartment of said pair being contiguous to said second wall part and both compartments of said pair communicating with one of said intake passages, a shaft supported for rotation in said inner casing and extending through said wall parts; sealing means interposed between said shaft and said i second wall part; a plurality of single impellers mounted on said shaft, said single impellers being operatively disposed for rotation in said coinpartments of said first wall part to develop predetermined positive liquid pressures therein and in said intermediate passage, the axial thrust of each of said single impellers in said compartments being balanced by another of said single impellers in said compartment in said rst wall part mounted to face in the opposite direction, and a pair of impellers mounted on said shaft on the intake chamber side of said second wall part, one impeller of said pair of impellers being operatively disposed in one compartment of said pair of compartments and the other impeller of said pair of impellers being operatively disposed in the other compartment of said pair of compartments, said pair of impellers cooperating to reduce the velocity of liquid flow into said pair of compartments below the velocity ow in said intake passages and to develop a predetermined liquid suction pressure in said intake chamber and a predetermined intermediate liquid pressure in said pair of compartments greater than said suction pressure, said intermediate pressure cooperating with said sealing means to substantially prevent back liquid flow from said intermediate passage to said intake chamber.

3. A centrifugal pump comprising: an outer vcasing having an inlet passageway and an outlet passageway for the flow of liquid therethrough and having an internal wall portion'dening an opening; an inner casingin said outer casing cooperating with said wall `portion to close said opening and divide said outer casing into separate intake and discharge chambers respectively communicating with said inlet and discharge passageways, said inner casing comprising first, second and third Wall parts, said first wall part defining a plurality of compartments and intake passages for said liquid, each said compartment communicating'with the intake passage hydraulically adjacent thereto and the last of said compartments communicating with saidy outlet passageway, said second wall part cooperating with said first wall part todevfine an intermediate passage contiguous to said second wall part and communicating with one of said compartments, said third Wall part cooperating with said second wall part to dene a pair of compartments on the intake'fchamber side of said second wall part, one compartment 'of said pair being contiguous to said second -wall part and both compartments of said pair oo mmunicating with one of said intakepassages, a shaft supported for rotation in said inner casing and extending through said wall parts; sealing means interposed between said shaft and said second wall part; a plurality of single impellers mounted on said shaft, said single impellers being operatively disposed for rotation in said compartments of said first wall part to develop predetermined positive liquid pressures therein and in said intermediate passage, and a pair of impellers mounted on said shaft on the intake chamber side of said second wall part and having inlets facing and cooperating with each other to balance the thrust developed by each of said pair of impellers, one impeller of said pair of impellers being operatively disposed in one compartment of said pair of compartments and the other impeller of said pair .of impellers being operatively disposed in the other compartment of said pair of compartments, said pair of impellers cooperating to reduce the velocity .of liquid flow into said pair of compartments below the velocity of iiow in said intake passages and to develop a predetermined liquid suction pressure in said intake chamber and a predetermined intermediate liquid pressure in said pair of compartments greater than said suction pressure, said intermediate pressure cooperating with said sealing means to substantially prevent back liquid flow from said intermediate passage to said intake chamber.

4. A centrifugal pump comprising: an outer casing having an inlet passageway and an outlet passageway for the flow of liquid therethrough, and having an internal wall portion defining an opening; an inner casing in said outer casing cooperating with said wall portion to close said opening and divide said outer casing into separate intake discharge chambers, respectively, communicating with said inlet and discharge pas'- saigeways, said inner casing comprising first, second and third wall parts, said iirst 'wall part defining a plurality of compartments and intake passages for said liquid, each said compartment communicating with the intake passage hydraulically adjacent thereto and the last of said compartments communicating with said outlet passageway, said second wall part cooperating with said rst wall part to define an intermediate passage -contiguous to said second wall part and av 99e. 9? su@ said musi well per@ eeeper `'me wish s 'd see- -ueueus se .se-@ seeen wel; Def-t end beth ,eem- Pssuuees ef sed esi? egulmueeetiue with `913e ,M .ssdtele Passages e snai@ suppelse@ for Ietmeuen seid meer easing and esseneine through sed well parte: sealing entier-Dese@ lee- .sw wsessi s t feud seid seeend wel eers; e R1 elify Aeff sle imrsellers mounted 101,1 saisi s!! .fsf eeen ei sais! plufelifey ef Asinele',rrlrlpel1ere .hevige e. Preeletesmiped eepeeiw, .seid single im- Re A u Wely sspesed fer-rotation@ 'ld elpertmelts e? .sessi tires well per-b t9 .deselee Dredetemeed positive liquid pressures @serein en@ in Seid @remediate Passage, ered a Puis -impelless eeeupted een .seid shaft ,en vthe issie-ilse @gember Aside ef .seeesd vWell part. @99h ef essi se?? ef @Pellets leaving a. capacity less @en sei@ pseseel' ed eepeity, one im.- Pelle 9i seid peil' Q f impellers being operatively speses .in @ne @warmest .ef seid peil .ef .egmpermeue @13d me@ @er impeller ef seid peir @f impellere being operatively disposed in the' @thee eenepesmess er .sid seis e? eemmreseeef seid pair ef impellels legepe ne'tereduee'fe veleeiey 0f liquid flew .iste ssi@ Pei? 9 1. ,messemeeee below' me velee-fey Q1? ew is .Seie im lie passages and te devel?? e vredeermiued lieuisl sei@ intake euriembe" au@ e predetermined mtemlediee 11911.11@ psesesre 111 Seid Heir eif eeseperemente ereeser then seid sue-f tien pressure sei@ istemediete Pressure 1.1- eresine with seid seeline ,Ineens te Westerwelle -prevent `bar .ek liquid w Lfm said mtergxiqie pssseee t9 Seid intese member# .EDWARD seeswssu suction pressure riu Refereneee Cited ie @he .0i this RePesi? STATES PATENTS Nsme Bete ebalq T-- Nov. 2, 19715 Hollander Jan. 10'J v1928 Mrh i', al, Dec. 26, 11933 Hollnder y Oct. 20; 1936 A T-'.i-.LTTT Apr' 157; FOREIGN PATENTS Country Date .Germany Feb. 20, 193.0

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